Various support frame and drive assemblies have been proposed for moving fabric covers or the like as a covering, examples of which are disclosed in U.S. Pat. Nos. 2,140,220 , dated Dec. 13, 1938; 2,668,586, dated Feb. 9, 1954; 4,424,685, dated Jan. 10, 1984; and 4,606,157, dated Aug. 19, 1986.
The support frame and drive assemblies disclosed in the first three mentioned patents for extending and retracting a cover or curtain, utilize endless loop sprocket chains, belts or cables connected to motor drives and to the cover for extending and retracting the covers. The drive systems in these patents are rather bulky, and the parallel flights of the endless drive chains, belts or cables are spaced apart a substantial distance from each other, thus requiring a substantial amount of space with support for the endless loop drive at opposite ends, thus making the arrangement bulky from an aesthetic standpoint for use in framing for an awning system over top of a patio, side walk restaurant, or attached over the top of a greenhouse, or the like. No support is provided for the endless loop drives throughout their lengths, and it is difficult to maintain the endless loops in tension at both sides of the awning member to evenly drive both sides of the awning member simultaneously to prevent cocking and binding of the leading edge of the awning member or covering, and the structures do not allow an awning to go around a curve.
The latter mentioned U.S. Pat. No. 4,606,157 discloses a curtain or shade for drawing across the inside of a greenhouse. In order to overcome the drawbacks of bulky endless loop drive systems, the opposite lateral edges of the shade are guided in track channels, which creates a substantial amount of friction drag. Cables are connected to the opposite front sides of the shade, and are guided in the same track channels as the shade edges, and extend forwardly from the shade and are wound onto respective constant torque spring loaded rollers at the far end of the shade support frame members. However, this system also has drawbacks, since as the shade is rolled from the roller, each lateral edge and forward cable has friction drag on it in the respective guide channels, which drag may be different for opposite edges due to dust, dirt, etc. built-up in the channels, and also the torque of the spring loaded rollers can change with age, thus giving a different pull to opposite front edges of the shade, causing the shade to bind in the guide channels.
While the support frame and drive assemblies shown in the prior art have generally been satisfactory for their intended purpose, for a certain length of time, none have solved the problem of how to provide a compact, strong support frame and compact drive assembly having a commonly driven drive assembly for opposite lateral edges of the awning, which stays in synchronization for constant even extension and retraction of the front edge of the awning, without cocking or binding, and which is substantially resistant to outside weather conditions.